Odorized gas and method for odorizing the same



2,8 7 2,304 Patented Feb; 3, 1959 ODORIZED GAS AND METHOD FOR ODORIZINGTHE SAME "John L. Eaton, Whitemarsh, Pa.;-andGeorgeEi Hihds,

Houston, Tex., assignors, by mesne assignments, to 'Pennsalt ChemicalsCorporationpa corporation of Pennsylvania I NoDrawing. ApplicationDecember 235-1953 Serial No. 400,098

18 Claims. (Cl. 48-195) This invention relatesto alkyl 'thioetherscontaining at least one tertiary alkyl. group, and relates also to theuse of these compounds as gas odorants.

Natural gas, thepropane and'butane fractions of liqui- 'fied petroleumgases, and-some types of 'manufactured Igases possess practically noinherent odor, and odorization of these gases, so that they will bedetectable at low concentrations'in the atmosphere, has been' practicedfor many years. :In the gas industry, it is standard practice to add acontrolled amount of a strongly odorifer'ous material to act as awarning'agent in the case of a gas leak, and many states have lawsrequiring that gas be odorized to a specifiedminimum level as a safetymeasure. "Adequate odorization is not only a safety measure but] resultsalso in substantial economies since pipe line leaks, which may amount inthe aggregate to considerable gas loss, may be promptly detected andrepaired. Also, these leaks would not be detected if the gas were notodorized.

Gas odorants in current use belong to the general category eitherof'merc'aptahs 'or organic sulfides. Odor'ants in either category may bepure compounds ormixtures, and may be used in concentrated form ordiluted with relatively inodorous materials. Mercaptans have a higherodor intensity but are easily oxidized by traces of oxygen in a pipeline to relatively inodorous disulfides. Organic sulfides are of lowerodor intensity than mercaptans, but arestable to pipe line oxidativeconditions so" that, if

added to the gas in sufiicient amountrthe odor Will'be' transmittedunimpaired over'long distances.

An odorant of acceptable quality'should be harmless and neither toxicnor nauseating, non-corrosive,-'chemically inactive, insoluble in water,inexpensive and readily available, burn completely without harmfulorodorous products of combustion, be stable and not adsorbed'by mains ormeters, and should possess a. penetrating odor similar to the artificialgas smell.

In accordance with the present invention, alkyl thioethers containinga'tertiary alkylgroup are used as sulfidetype odorants, possessing theoxidation stability common to thioethers and possessing ahigher odorintensity than other alkyl thioethers.

Among the compounds whichareuseful asfodorants in accordance with theinvention maybe mentioned tertiary butyl, methyl, ethyl, propyl, andisopropyl sulfides, and tertiary amyl, methyl, ethyl, propyl, andisopropyl sulfides. Other compounds of this type may also be employed,the alkyl chain length being limited only by the vapor pressure of thecompounds, i. e., the compounds must have a vapor pressure sufficientlyhigh-that thecornpound may be vaporized into the gas stream in a pipeline in amount suificient for adequate odorization. It is also essentialthat a tertiary carbon atom be directly linked to the sulfur atom.

In practice, odorization is usually effected by means of an injectiontype o dorizer in which-the odorant is pumped into the gas stream andvaporized,"or a metered portion of gas is passed over a wick andsaturated with the odor- .ant. @These are conventional 'expedientsin-the art, and any othertype-of'odorizing equipmentmay'alsobe'empl'oyed. The odorant is generally added-tothe gas-in a pipeline at the rate of about 0.2 pound to 3.0 pounds fofodorant per millioncubic feet of gas with the preferredrate being about 1.5 poundsofodorantpermillibn cubic feet of gas.

The invention will be further illustrated by reference to the followingspecific examples:

EXAMPLE 1 Preparation of tertiary butyl ethyl sulfide A two gallonautoclave was charged with 1261 grams (14 mols) of tertiarybutyl'mercap'tan, 950 grams (14.72 mols) of ethyl chloride and 616 grams(-15.4mols)' of sodium hydroxide dissolved in 2308 grams of Water,-this'being'the calculated amount of water to yield a saturated salt solutionif the reaction goes to completion. The reagents were chilled beforecharging and the autoclave was rapidly closed after chargin wascompleted. The autoclave was then heated, with continuous agitation, toa temperature of 150 C. in'45 minutes, maintained at a temperature of150 C; for 15 minutes, rapidly cooled, and discharged, usingconventional precautions to avoid loss of volatile components.

After distillingofi unreactedethylchloride, theoil layer was steamdistilled, dried azeotropically," and fractionally-distilled. Ethylchloride and mercaptan heads were removed and 1511 grams of as acutboiling at 119 to 119.5 C.

EXAMPLE 2 Preparation of tertiary bzztyl isopropyl sulfide A two gallonautoclave was charged with 910 grams of tertiary butyl mercaptan, 800grams of isopropylchloride, and a solution of 450 grams of sodiumhydroxide in 2850 grams of water. The autoclave was heated to atemperature of 126 C;'in 40 minutes and was held at--a temperature of125 to 135 C. for minutes, during which time the pressure varied betweenand 100 p. s. i.-g. The autoclave was cooled to a temperature'of 25 C.and discharged. 1,580 grams of crude oil layer were recovered having aspecific gravity of 0.840.

The Engler distillation of this layer was as follows:

product were obtained C. C. IBP 37.0 60 55 1 39.0 70 64 5 40 80 "'98 1042 132 20 43.5 30 45 FBP 141 40 48 Re'cov 97 50 50.5

' 1,163 grams of neutral crude product were fractionally distilled.After removin un'reaeted isopropyl chloride arid tertiary butylmercaptan, 142.5 grams of tertiary biityl isopropylsulfidewererecovered, boiling at l 3 2 C.*'-and having a specific gravity of0.815.

EXAMPLE '3 Preparation of tertiary amyl ethyl sulfide A twogallon-autoclave was charged withl050""g'r'an1s (10.1 mols) of tertiaryamyl mercaptan, 450 grains (11.2 mols) or sodium hydroxide, and 660grams (10.2 mols) of ethyl'chloride in 2000 g'rams'of water. The' autoclave was then-heated, while subjecting the'mixture to agitation. Thetemperature was-maintained"at"l30to C. for two hours, during which timethe pressure varied from 80 to 100 p: s. ifig. The autoclave w'as cooledto 24 C. (pressure 5 p. s. i. g), vented, and discharged. 1,482 grams ofoil layer, and 2,646 grams of saline solution were obtained. Titrationof the water layer indicated that 77.5% of the total sodium hydroxide'had been consumed. The crude oil layer had a specific gravity of 0.831and the Engler distillation of this layer was as follows:

1110.5 grams of crude product were fractionally distilled, and afterdistilling off the unreacted mercaptan and ethyl chloride, 465 grams oftertiary amyl ethyl sulfide were recovered as a clear colorless liquidboiling at 146 to 148.5" C. and having a specific gravity of 0.840.

EXAMPLE 4 A room test procedure was used to estimate odor thresholds ofvarious materials. The test consisted of the vaporization of successiveincrements of a dilute ethanolic solution of the odorant to be evaluatedinto a nitrogen stream which was passed at a uniform rate into anelectric fan which circulated the odor throughout a closed room, theexact time of each injection being recorded. This room had a volume of1233 cubic feet. A panel or six observers was seated at random in theroom prior to the start of the test, in clear view of a clock. At theend of the test, each observer independently recorded the earliest timeat which odor had become apparent to him. The odorant concentration inthe room at any given time was calculated from the known injectionschedule of the odorant solution and thus the threshold concentrationfor each observer was determined.

As shown by the following table, tertiary butyl ethyl sulfide was ratedas stronger than mixed lower alkyl ethyl sulfides by three of the fiveobservers, with one observer considering the intensities equal and oneconsidering the tertiary butyl ethyl sulfide as weaker. Four out of thesix observers considered tertiary butyl methyl sulfide as equal to thecorresponding ethyl sulfide, with one rating the methyl homologuestronger and onerating it weaker:

I One observer falls to detect at indicated level. 1 Two observers fallto detect at indicated level.

Comparisons between tert-BuSET, tert-AmSET, and mixed amylmethylsulfides were made, using an apparatus which presents, to the nose ofthe observer, a definitely known concentration of odorant in gas-air'mixture. The tests, as originally conducted, were duplicated two dayslater, but with the order of presentation of the odorants reversed, tocancel out any efiect the order of presentation may have on theobservations.

Threshold, lbs/10 C. F.

Odorant Observer A Observer B order as order order as order listedreversed listed reversed tert-BuSET 0. 55 0.3 0. 4 0. 2 tert-AmSET 1. 50.65 0.2 0. 3 Mixed AmSMe 2. 7 1. 1 2. 4 0. 4

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention without departingfrom the spirit thereof, and the invention includes all suchmodifications.

We claim:

1. A method of odorizing a gas which comprises mixing the gas to beodorized with a compound having the structure in which R is selectedfrom the group consisting of tertbutyl and tert-amyl radicals and R isselected from the group consisting of methyl, ethyl, propyl, andisopropyl radicals.

2. A method of odorizing a gas which comprises mixing the gas to beodorized with a compound having the structure in which R is a tert-butylradical and R is selected from the group consisting of methyl, ethyl,propyl, and isopropyl radicals.

3. A method of odorizing a gas which comprises mixing the gas to beodorized with a compound having the structure in which R is a tert-amylradical and R is selected from the group consisting of methyl, ethyl,propyl and isopropyl radicals.

4. A method of odorizing a gas which comprises mixing the gas to beodorized with a compound having the structure in which R is selectedfrom the group consisting of tertbutyl and tert-amyl radicals.

5. A method of odorizing a gas which comprises mixing the gas to beodorized with a compound having the structure R-S-CH in which R isselected from the group consisting of tertbutyl and tert-amyl radicals.

6. A method of odorizing a gas which comprises mixing the gas to beodorized with a compound having the structure in which R is selectedfrom the group consisting of tertbutyl and tert-amyl radicals.

7. A method of odorizing a gas which comprises mixing the gas to beodorized with a compound having the structure in which R is selectedfrom the group consisting of tertbutyl and tert-amyl radicals.

8. A method of odorizing a gas which comprises mixing the gas to beodorized with tert-butyl ethyl sulfide.

9. A method of odorizing a gas which comprises mixing the gas to beodorized with tert-butyl methyl sulfide.

10. A method of odorizing a gas which comprises mixing the gas to beodorized with tert-butyl isopropyl suifide.

11. A method of odorizing a gas which comprises mixing the gas to beodorized with tert-butyl propyl sulfide.

12. A method of odorizing a gas which comprises mixing the gas tobeodorized with tert-amyl ethyl sulfide.

13. A method of odorizing a gas which comprises mixing the gas to beodorized with an alkyl thioether having a tertiary carbon atom linked tothe sulfur atom and having a vapor pressure sufficiently high that thecompound may be vaporized into a gas stream in a pipe line in amountsutficient for adequate odorization.

14. A method of odorizing a gas which comprises mixing the said gas withan alkyl thioether having a tertiary carbon atom linked to the sulphuratom and having a vapor pressure sufficiently high that the compound maybe vaporized into the said gas, the said thioether being present at aconcentration of 0.2 to 3 pounds per million cubic feet of gas.

15. An odorized gas comprising a major proportion of a member of theclass consisting of natural gas, man ufactured gas and mixtures thereof,and a minor proportion of an alkyl thioether having a tertiary carbonatom linked to the sulphur atom, said thioether being present at aconcentration of 0.2 to 3 pounds per million cubic feet of gas.

16. An odorized gas comprising a major proportion of a member of theclass consisting of natural gas, manufactured gas, and mixtures thereof,and a minor proportion of an organic sulfide having the structure inwhich R is selected from the group consisting of tertbutyl and tert-amylradicals and R is selected from the group consisting of methyl, ethyl,propyl, and isopropyl radicals, said organic sulfide being present at aconcentration of 0.2 to 3 pounds per million cubic feet of gas.

17. An odorized gas comprising a major proportion of a member of theclass consisting of natural gas, manufactured gas and mixtures thereof,and a minor proportion of an organic sulfide having the structure inwhich R is a tert-butyl'radical and R is selected from the groupconsisting of methyl, ethyl, propyl, and isopropyl radicals, saidorganic sulfide being present at a concentration of 0.2 to 3 pounds permillion cubic feet of gas.

18. An odorized gas comprising a major proportion of a member of theclass consisting of natural gas, manufactured gas and mixtures thereof,and a minor proportion of an organic sulfide having the structure RSR inwhich R is a tert-amyl radical and R is selected from the groupconsisting of methyl, ethyl, propyl and isopropyl radicals, said organicsulfide being present in the gas mixture at a concentration of 0.2 to 3pounds per million cubic feet of gas.

References Cited in the file of this patent UNITED STATES PATENTS Bureauof Mines, page 17.

1. A METHOD OF ORDORIZING A GAS WHICH COMPRISING MIXING THE GAS TO BEODORIZED WITH A COMPOUND HAVING THE STRUCTURE.